Process of manufacturing nonwoven fabrics



Aug. 10, 1965 R. E. CHARLTON, JR., ETAL PROCESS OF MANUFACTURING NONWOVEN FABRICS Filed Feb. 9, 1961 INVENTORS Plan/Q20 E C/m/u ra/v, JR RICH/9RD E H0050 /v, JR

BY MAM, M ATTORNEYS United States Patent 99,167 PRES itiANUFAiITURlNG NQN- WGVEN FABREQS Richard E. Charlton, .irz, Fairfax, Alla and Richard E.

ti-risen, 31"., West Point, Gm, assignors to West Point- Pepperell, inc, a corporation of Georgia Filed Feb. 9, 1961, Se". No. 88,5?24 4 Claims. (Cl. 28-72..2)

This invention relates to the manufacture of nonwoven fabrics, and particularly to the manufacture of nonwoven fabrics having high internal bond strength and resistance to delamination. Fabrics of this type are particularly useful in the manufacture of high pressure laminates, fire hoses, conveyor and transmission belts, filters, tire chafer fabrics, backing for vinyl and other upholstery fabrics, shoe fabrics, wiper cloths, and numerous other applications wherein strength in direction transverse to the fabric surfaces is important.

It is known that carded webs exhibit high strength primarily in a single direction. By cross-laying carded webs, nonwoven structures exhibiting high strength in two or more directions may readily be obtained. It is also known, for example as in Wilson et al. Patent 2,477,675, to airlay nonwoven fabrics by utilizing an air stream to deposit fibers in random fashion, whereby fabrics exhibiting high strength in all directions in the plane of the fabric surface may be obtained.

It is known, further, that nonwoven fabrics may be needle punched, thereby disposing some of the fibers in direction normal to the fabric surfaces. This offers the possibility of increasing the internal bond strength of the fabric, particularly if the vertically oriented fibers are fixed in such disposition. As a practical matter, however, the improvement of internal bond strength by needle punching presents serious diificulties.

For example, it will be readily understood that in the manufacture of nonwoven fabrics, the initial deposition of the fiber web is critical, it being essential for most applications to insure uniformity of thickness, fiber arrangement and the like. It has been found that if a newly deposited and unbonded fiber web is subiected to conventional needle punching, the fibers of the web are seriously disarranged, producing such lack of uniformity, discontinuity and irregularity as to render the web commercially unacceptable. Also, such fibers as are vertically oriented do not contribute materially to internal bond strength, since they are not bonded or otherwise engaged to adjoining fibers. On the other hand, if a fiber web is bonded before needle punching, other difficulties are encountered. It has been found that fibers of bonded webs are frequently locked together adequately to resist relative displacement, whereby fibers engaged by the needles of a needle loom are broken. The broken fibers, while they may be vertically oriented by needle punching, do not contribute materially to internal bond strength. Also, conventional bonding agents in nonwoven fabrics may foul the needles or unduly load the needle loom, causing damage to the machine and/or necessitating excessively slow operation.

A principal object of the present invention is to provide an improved and superior method of manufacturing nonwoven fabrics, wherein some of the fibers are reoriented by needle punching, without disturbing the desired configuration and arrangement of the remaining fibers. A related obiect is to produce nonwoven fabric in which some fibers are disposed normal to the fabric surfaces, and firmly locked in such arrangement.

Another object of the invention is to provide a novel and efficient process for the production of nonwoven fabrics having high internal bond strength and resistance to elamination. Further objects will be in part evident and in part pointed out hereinafter.

in accordance with the present invention, a fiber web of desired structure is initially subjected to a very light bonding treatment, just adequate to permit handling the web without distortion and needle punching the web without more than local disruption of the fiber arrangement. The lightly bonded web is then needle punched in conventional fashion. It has been found that this operation may be performed efiiciently, without external support of the web. Finally, the needle punched web is bonded to the desired degree, binding the fibers in the initially deposited and needle punched arrangement.

The following examples are illustrative of the invention. Throughout the specification and claims, the parts and percentage figures are expressed on a weight basis unless otherwise stated.

Example 1 A mixture of crimped heat-set nylon staple fiber and 10% rayon staple fiber is carded on a modified woolen card, and the card Web crosslaid to produce a fiber web Weighing three ounces per square yard. The crosslaid web is lightly bonded by impregnation apparatus of the type shown in Payne Patent 2,877,739, and then dried. The bonding agent is a dilute aqueous dispersion of butadiene acrylonitrile copolymer (Hycar 1572), with minor additions of soap and antioxidant, diluted to three percent solids content.

The crosslaid web is saturated with the dilute binder dispersion, the excess removed therefrom by vacuum, and then dried. The binder pickup in the initial light bonding treatment is approximately three percent on a dry web basis, the dried prebonded web weighing 3.1 ounces per square yard.

The prebonded web is then needle punched by means of a conventional Hunter inch Fiberlocker needle loom, equipped with regular barb, nylon No. 32 needles. The needle penetration of the web is adjusted to one inch point penetration, whereby the first several barbs pass through the Web. The web speed is adjusted to effect 200 punches per square inch. The lightly bonded web requires no special support for the needle punching operation, and fibers are reoriented into direction normal to the web surfaces, without excessive disruption of the web.

The prebonded and needled web is then again impregnated by means of the apparatus of Payne Patent 2,877; 739, using a 60% solids aqueous dispersion of butadiene acrylonitrile copolymer, containing minor amounts of zinc oxide, sulphur, accelerator and antioxidant. The binder pickup (dry weight basis) in the rebonding step is approximately fifty-five percent. The rebonded web is dried on cans at 280 F. for two minutes, and rolled up hot to complete the cure. The weight of the final product is 4.7 ounces per square yard. The product exhibits excellent resistance to delamination, and is particlularly useful as backing fabric for vinyl sheets, adapted for use as automotive and furniture upholstery.

Example 2 A random web of bright (no delusterant) viscose rayon staple fiber, 1% inches X 3 denier, is airlaid by means of apparatus of the type disclosed in Wilson et al. Patent 2,478,148, to produce a fiber Web weighing two ounces per square yard. The airlaid web is lightly prebonded by impregnation with a dilute (5%) aqueous dispersion of nitrile rubber (Hycar 1572) in water, using apparatus of the type shown in Payne Patent 2,877,739. The impregnated web is extracted by vacuum and dried, the binder pickup in the prebonding treatment being approximately 5%, the prebonded and dried web weighing 2.1 ounces per square yard. The prebonded Web is then needle punched as in the previous example, applying 200 punches per square inch.

The prebonded and needled web is then rebonded by means of impregnation apparatus of the type disclosed in Payne Patent 2,877,739, using two passes through the following bonding composition:

The binder pickup (dry weight basis) in the rebonding step is approximately 300% The rebonded web is dried on cans at 250 F., cooled and rolled up, the final product weighing 8 ounces per square yard. The product is particularly useful as a tire chafer fabric, and exhibits approximately 40 pounds per inch internal bond strength, in delamination tensile tests.

The process is illustrated in the accompanying drawing, in which:

FIGURE 1 is a diagrammatic sketch illustrating an exemplary embodiment of the process of the invention, and

FIGURE 2 is a sectional view, on enlarged scale, of a fabric made by the process of FIGURE 1.

As shown in FIGURE 1, a fiber web 10 is conducted through a dip tank 12 containing a prebonding bath 14, Where it is thoroughly impregnated with the prebonding composition, and excess liquid is removed therefrom by the suction box 16 The wet web is then conducted through an oven or dryer 1S, and then conducted through a conventional needle loom 20, wherein it is supported by the underlying support 22 while punched by conventional barb needles 24.

After needle punching, the fabric is conducted successively through dip tanks 26 and 28, containing respectively rebonding baths 30 and 32. Excess impregnant picked up from the rebonding bath 30 is removed by suction box 34, and excess impregnant picked up from the rebonding bath 32 is removed by suction box 36. The rebonded web is then dried on dry cans 38 and rolled up at 40. The finished fabric 42 is illustrated in FIGURE 2, wherein 44 represents the reoriented fiber bundles resulting from the needle punching.

As will be evident, the invention may be utilized with all common textile fibers, natural and synthetic, and blends thereof, including cotton, viscose rayon, acetate rayon, nylon, Dacron, Orlon, Acrilan and Dynel. The initial fiber web may be formed in any conventional manner, and crosslaid, plied or otherwise arranged. The web weight, prior to the initial stabilization, step will normally range from 1 to 8 ounces per square yard, although lighter and heavier webs may be used.

Binders useful in the invention include natural and synthetic materials, such as polyvinyl alcohol, starch, polyvinyl chloride and copolymers thereof, polyvinylidene chloride and copolymers thereof, natural rubber, nitrile rubber, chloroprene rubber, styrene elastomers and plastics, elastomeric acrylate polymers, and resinous materials including resorcinol formaldehyde and melamine formaldehyde. The same of different binder materials may be utilized in the prebonding and rebonding steps.

' combined weight of fibers and binder.

4 The prebonding binder may be selected to promote the adhesion of a different rebonding binder.

The binder may be applied in any conventional manner, as by impregnation, spraying, powdering with subsequent fusion or solution, or the like. The total quantity of binder applied in the prebonding and rebonding steps, normally, will be from about 25% to about of the The quantity of binder material applied in the prebonding, or initial stabilization step, is minor, and desirably as little as possible while effecting the desired function. In nearly all cases, the minor quantity of binder appliedin the prebonding step will be less than 10% of the weight of the product fabric.

In the needle punching operation, it is necessary only to reorient enough fibers to materially improve the resistance of the product fabric to delamination. It has been found that 50 punches per square inch is effective for such purpose. The increase in internal bond strength improves with the degree of needle punching, but little increase is achieved by exceeding about 500 punches per square inch.

The rebonded product may be dried, and depending on the character of the binder and its intended purpose, also partially or completely cured. Drying and curing may be effected simultaneously, or in separate steps.

It will thus be seen that there has been provided by this invention a method in which the various objects hereinbefore set forth, together with many practical advantages, are successfully achieved. As various possible embodiments may be made of the novel features of the above invention, all without departing from the scope thereof, it is to be understood that all matter hereinbefore set forth is to be interpreted as illustrative, and not in a limiting sense.

We claim: I

1. A process of manufacturing nonwoven fabrics comprising the steps of applying a minor quantity of binder material to a nonwoven fiber web to partially stabilize the web uniformly throughout its thickness, drying the web, needle punching the initially stabilized web to orient some of the fibers in direction normal to the web surfaces, and then applying a major quantity of binder material to the needle punched web.

2. Process as defined in claim 1, wherein the total quantity of binder represents from about 25% to about 90% of the combined weight of the fibers and binder, of which up to about 10% is applied in the initial stabilization step.

3, Process as defined in claim 1, including the final step of drying and curing the binder material.

4. Process as defined in claim 1, wherein from about 50 to about 500 punches per square inch are applied in the needle punching step.

References Cited by the Examiner UNITED STATES PATENTS 2,249,888 7/41 Dodge 28--79 2,314,162 3/43 Reinhardt 1. 28 72.2 2,339,431 1/44 Slayter 161165 2,377,564 6/45 -Lundgren 2872.2 2,794,759 6/57 Dildilian 28-722 2,970,365 2/61 Morgenstern 156-148 XR 2,978,785 4/61 Wenzell et al. 2872.2 2,996,411 -8/6l- Lauterbach 2879 FOREIGN PATENTS 556,186 9/43 GreatBritain.

EARL M. BERGERT, Primary Examiner.

CARL F. KRAFT, Examiner. 

1. A PROCESS OF MANUFACTURING NONWOVEN FABRICS COMPRISING THE STEPS OF APPLUING A MINOR QUANTITY OF BINDER MATERIAL TO A NONWOVEN FIBER WEB TO PARTIALLY STABILIZE THE WEB UNIFORMLY THROUGHOUT ITS THICKNESS, DRYING THE WEB, NEEDLE PUNCHING THE INITIALLY STABLIZED WEB TO ORIENT SOME OF THE FIBERS IN DIRECTION NORMAL TO THE WEB SURFACES, AND THEN APPLYING A MAJOR QUANTITY OF BINDER MATERIAL TO THE NEEDLE PUNCHED WEB. 